This invention relates to a system of positive identification for individual ones of a large number of things, such as animals, objects or other things. More specifically, the invention concerns a system wherein an identifying device is implanted within or imbedded beneath the surface of the thing to be identified so that there is no visual indication of the presence of the identification device. In such systems, positive identification is achieved by the use of an external probe which is brought into close proximity with the implanted or imbedded identifying device and a non-visual contact is made between the probe and the identifying device. Such identification systems are extremely useful in the identification or verification of identification of livestock, particularly thoroughbred horses, and other valuable objects such as boats, luggage, books, etc.
It is known in the applicable art to employ identification systems which include an implantable or imbeddable identification device and a remote probe which is brought into proximity with the identification device for generating a representation unique to the identification device, and hence, to the animal, object or thing to be identified in which the identification device is implanted or imbedded. For example, U.S. Pat. No. 3,689,885 to Kaplan et al for an inductively coupled passive responder and interrogator unit having multidimension electromagnetic field capabilities discloses an interrogator-responder system wherein the electromagnetic energy generated by an interrogator or probe is applied to an identification device in the form of a responder tag. A signal is generated by the responder tag in response to the electromagnetic energy transmitted from the interrogator and is retransmitted back to a receiver in the interrogator, the retransmitted signal containing information on the identity of the responder tag, and hence the thing to which it is attached, which information is processed and displayed for identification purposes.
U.S. Pat. No. 3,706,094 to Cole et al for an electronic surveillance system discloses a similar system wherein the identification device includes a substrate of piezoelectric material having coded information stored within it. The electromagnetic energy transmitted by a remote probe brought into proximity with the identification device is converted into acoustic energy and then back to electromagnetic energy and retransmitted back to a receiver in the probe after being modulated by the coded information. Still another approach to the problem of identification is disclosed in U.S. Pat. No. 3,859,624 to Kriofsky et al for an inductively coupled transmitter-responder arrangement. Kriofsky also discloses identification systems employing an interrogator and responder tag wherein the electromagnetic energy is transmitted from the interrogator to the responder tag and the signal is retransmitted from the responder tag to the receiver in the interrogator for identifying the responder tag and the thing to which it is affixed.
The foregoing systems as well as other systems in the prior art for use in the remote identification of things all require that an energy signal be transmitted from a probe to an implanted or imbedded or otherwise attached identification device and that an energy signal then be retransmitted from the identification device back to a receiver in the probe. This necessitates the use of two transmission-reception channels as well as transmission and reception circuitry in both the probe and identification device. It also requires that the identification device which is implanted, imbedded or attached, include one or more active devices and/or one or more energy storage devices for providing an energy signal responsive to the signal transmitted from the probe for retransmission back to a receiver in the probe. Since it is necessary to make the identification device as small as possible, particularly in cases where it is to be implanted beneath the skin of an animal, it is desirable to eliminate the need for active and energy-storing devices which restrict the minimum size and weight of such devices. Moreover, it is also desirable to eliminate the use of active and energy-storing devices which generate heat and electromagnetic radiation as such emissions may be harmful to the animal or object in which the device is implanted. In addition, conventional remote identification systems are susceptible to interception of signals by unwarranted observers or listeners, a feature resulting in low security aspects.